1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device.
2. Background Art
A demand for miniaturization of a semiconductor device is addressed until now by methods such as shortening of exposure wavelength and increase in NA (numeric aperture) of an exposure lens in a photolithography process. However, it is becoming difficult to address a demand for fast-paced further miniaturization of a semiconductor device by conventional methods such as shortening of exposure wavelength and increase in NA of an exposure lens.
Consequently, a technique called double patterning is being proposed. Briefly, this technique is an application of multiple exposure. For example, exposure is performed on a resist film once with a mask of a rough pattern. The mask is displaced and exposure is performed again. After that, development is performed.
In this technique, however, precision of alignment of an exposure apparatus at the time of multiple exposure is strictly requested and it is difficult to realize the technique in practice.
A method for forming a fine pattern of a silicon oxide film is also proposed (for example, Japanese Patent Laid-Open No. 1991-270227).
The method will be described as follows.
First, a resist pattern is formed at low pitches on a substrate to be processed. The resist pattern itself has a width corresponding to a predetermined pitch.
Next, a silicon oxide film is formed so as to cover at least the resist pattern.
Further, the silicon oxide film is etched so that the silicon oxide film remains only on both sides of each of the resist patterns. A gap of a predetermined pitch is formed between the silicon oxide films on both sides of neighboring resist patterns.
Subsequently, the resist pattern sandwiched by the silicon oxide films is selectively removed to make the silicon oxide films on both sides remain. As a result, the remaining silicon oxide films are arranged at intervals of the predetermined pitch. That is, a fine pattern having an interval of the pitch which is the half of the low pitch of the initial resist pattern is formed in the silicon oxide film.